A folding-type (collapsible) cellular telephone terminal, such as a folding-type cellular phone or a folding-type PHS (personal handyphone system) phone, has two body casings coupled together with a hinge portion. Printed circuit boards having electronic components mounted thereon are housed inside the individual body casings, and are connected together with a flexible printed circuit board. To make the folding-type cellular telephone terminal compact, the flexible printed circuit board is required to have a sufficiently small width. Moreover, as disclosed in Japanese Patent Application Laid-Open No. H1-89845, to prevent damage, such as breakage of conductors, resulting from the folding and unfolding of the body casings, the flexible printed circuit board arranged in the hinge portion is wound in a helical shape. Thus, the flexible printed circuit board is required to have a smaller width.
However, as folding-type cellular telephone terminals are furnished with increasingly advanced functions, the number of conductors formed as a conductor pattern on the flexible printed circuit board tends to increase. This makes it increasingly difficult to arrange the flexible printed circuit board in the body casings. This problem can be overcome by the use of a double-sided flexible printed circuit board having conductor patterns formed on both sides. However, a double-sided flexible printed circuit board is thicker than a single-sided one, and therefore the conductor pattern on the outer side receives a stronger tensile force when the flexible printed circuit board is bent. This leads to lower durability against the folding and unfolding of the body casing.
Moreover, a device, such as a folding-type cellular telephone terminal, that employs digital circuits and thus uses a clock pulse, tends to emit pulse noise, making the device a noise source. Noise is propagated either by being radiated through the air or by being conducted by a power or signal line. Where wiring is achieved by the use of a flexible printed circuit board, noise is propagated, by being conducted by the flexible printed circuit board, to other printed circuit boards having electronic components mounted thereon. Moreover, the flexible printed circuit board itself may act as an antenna, receiving noise being radiated through the air and propagating it to the other circuit boards. Such noise can be suppressed by shielding the flexible printed circuit board, but it is not easy to shield it, since it is bent frequently.